<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>let const应用</title>
    <style>
        body {
            padding: 50 0 0 150px;
        }
        
        .btn {
            width: 100px;
            height: 100px;
            margin-right: 20px;
            font-size: 80px;
            cursor: pointer;
        }
    </style>
</head>

<button class="btn ">0</button>
<button class="btn ">1</button>
<button class="btn ">2</button>


<body>
    <script>
        //重复声明 变量提升 暂时性死区 window对象的属性和方法  块级作用域
    </script>
</body>

</html>